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LittleBits Mixer

Discussion in 'General Electronics Chat' started by 4pyros, Apr 18, 2014.

  1. 4pyros

    4pyros Well-Known Member Most Helpful Member

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    Thanks for taking the time to decipher their web page to at least take a look at the other modules.
     
  2. 4pyros

    4pyros Well-Known Member Most Helpful Member

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    I know that, its just a figure of speech.
     
  3. 4pyros

    4pyros Well-Known Member Most Helpful Member

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    Yes but it works
     
  4. dave

    Dave New Member

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  5. ronsimpson

    ronsimpson Well-Known Member Most Helpful Member

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    There are a number of odd things. Like the volume control on the speaker amplifier. Good thing is the amp is AC coupled.
    This is the bottom line. It works for this application. Not what I would have designed. But it works. Not on external audio. But it works.
    Looking back it looks (not good). Back when the first "555" oscillator was designed and not knowing what the future would bring the system probably looked good.

    I wish I could see what tomorrow will bring. I can see the past.
     
  6. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    It's a perfectly valid volume control, and is quite often used in mixers - however, in this case it's a further example of design with little or no understanding of what they were doing. The entire opamp stage with volume control isn't needed at all, it actually gives a negative gain of ten, and from there down to infinity, plus it's fed from a low impedance buffer - it could be more sensibly replaced with a simple pot and series resistor, saving an opamp and the bis components etc.
     
  7. 4pyros

    4pyros Well-Known Member Most Helpful Member

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    Yes but the speaker and amp may not be the only output on the signal line. It has a pass thru connector that could have other things hooked up to it like motors and lights or more logic stuff, so it is buffered from the signal line.
     
  8. tvtech

    tvtech Well-Known Member Most Helpful Member

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    So glad I stayed out of this one :)...until now.

    So brilliant to see Members sparring and all and still being friendly to each other. Love it.

    Regards,
    tvtech
     
  9. 4pyros

    4pyros Well-Known Member Most Helpful Member

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    Oh but you did chime in at post 40
    Just wish others were interested in giving there thoughts.
     
  10. Little Ghostman

    Little Ghostman Well-Known Member Most Helpful Member

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    I am just watching and getting idea's, there is obviously a market. Modules to make sound that can plug into each other, modules able to connect to other's with say light, and Led cubes and drum machines.... Very interesting, I am looking for an angle for School to add to my list of things I sell.
    I didnt think of modules before, inputs to the Led cubes to make them sound to light via different avenues and not just a mic. I cant see it yet but I am sure there is something here I can use :D, dont get me wrong I am not money orientated but I like the whole business thing and the record keeping etc etc. Business appeals to my OCD and building stuff to sell appeals to my creative side
     
  11. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    You've misunderstood, the buffer is fine - it's the opamp following it (which only gives negative gain anyway) that's a total waste.
     
  12. 4pyros

    4pyros Well-Known Member Most Helpful Member

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    Ya seems to only be there for the volume control, but would it bring the positive only signal back to above and below 0 volts?
     
  13. 4pyros

    4pyros Well-Known Member Most Helpful Member

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    OK in trying to do some basic testing to day I found a program called DSSF3 with a signal generator and an oscilloscope.
    The web site is; http://www.ymec.com/products/dssf3e/
    The idea is to make waveforms from the computer to send into the littlebits mic module and use the headphone out of the littlebits speaker module hooked up to the mic input of the laptop to see the waveforms on the oscilloscope program.
    But I seem to have some ground loop problems and maybe some software issues.
    I will keep trying to get this to work.
     
  14. 4pyros

    4pyros Well-Known Member Most Helpful Member

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    OK I can look at waveforms from my sons iphone with the oscope on my laptop.
    Just using the mic input and speaker output modules the system will pass sign waves. Abit distorted though.
    Adding the mixer module in between I still get a shin wave but with a little more distortion and a dip one the top of the falling edge on the positive cycle.
    All and all better than I thought it would be, thought it would square the wave off.
    And it definitely works good enough for a kids toy.
    I think I will start making some of my own modules now that I have a better understanding of what I am working with.
     
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  15. 4pyros

    4pyros Well-Known Member Most Helpful Member

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    Last piece to the puzzle.
    The schematic for the mic input module.
    Look at this mess. Love the diode on the output of the buffer opamp.
     

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  16. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    No, there's no where in the circuit at all that does that anyway, and no reason for it to do so.
     
  17. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    Nothing wrong with that - it's there for a good reason.

    Presumably it's a modulator?, giving 'dalek' type effects etc. to the voice from the mike?.
     
  18. 4pyros

    4pyros Well-Known Member Most Helpful Member

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    I will have to look that up, thanks
     
  19. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    If I recall correctly it's called 'ring modulation'?, although I'm not sure that's exactly what it's doing.
     
  20. 4pyros

    4pyros Well-Known Member Most Helpful Member

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    OK I found this on dalek type effects, from a wiki page;
    This was done using transformers and diodes at the time to modulate the audio at 30Hz.
    I dont think that single diode would come close to this, but sounds like a net effect I would love to try.
     
  21. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    Not the single diode, the longtailed pair that the signal rectified by the diode is controlling.
     

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